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math
Find the smallest positive integer $y$ which satisfies the congruence $56y + 8 \equiv 6 \pmod {26}$.
6
33
1
math
Given a sequence $\left\{a_n\right\}$ with the sum of the first $n$ terms $S_n=n^2+2n$, and a sequence $\left\{b_n\right\}$ satisfying $3^{n-1}b_n=a_{2n-1}$, $(1)$ Find $a_n, b_n;$ $(2)$ Let $T_n$ be the sum of the first $n$ terms of the sequence $\left\{b_n\right\}$, find $T_n.$
\dfrac{15}{2}- \dfrac{4n+5}{2\cdot3^{n-1}}
113
26
math
Altitudes $\overline{AX}$ and $\overline{BY}$ of an acute triangle $ABC$ intersect at $H$. If $\angle BAC = 53^\circ$ and $\angle ABC = 82^\circ$, then what is $\angle CHY$?
45^\circ
60
4
math
Compute $(\cos 195^\circ + i \sin 195^\circ)^{36}.$
-1
26
2
math
A certain shopping mall held a promotion during the "May Day" period, and according to the total amount of one-time purchases by customers based on the marked prices of the goods, corresponding discount methods were stipulated:<br/>① If the total amount does not exceed $500, no discount will be given;<br/>② If the tota...
910
206
3
math
Three sides \(OAB, OAC\) and \(OBC\) of a tetrahedron \(OABC\) are right-angled triangles, i.e. \(\angle AOB = \angle AOC = \angle BOC = 90^\circ\). Given that \(OA = 7\), \(OB = 2\), and \(OC = 6\), find the value of \[ (\text{Area of }\triangle OAB)^2 + (\text{Area of }\triangle OAC)^2 + (\text{Area of }\triangle OBC...
1052
136
4
math
Given the function $f(x)=A\cos(\omega x + \varphi)$ defined on $\mathbb{R}$, with $A>0$, $\omega>0$, and $|\varphi| \leq \frac{\pi}{2}$, satisfies the following conditions: the maximum value is 2, the distance between two adjacent minimal points of the graph is $\pi$, and the graph of $f(x)$ is symmetric about the poin...
\left[-1, \frac{2\sqrt{2} + 1}{2}\right]
228
22
math
In the geometric sequence $\{a_n\}$, where $a_2a_5=-\frac{3}{4}$ and $a_2+a_3+a_4+a_5=\frac{5}{4}$, calculate $\frac{1}{a_2}+\frac{1}{a_3}+\frac{1}{a_4}+\frac{1}{a_5}$.
-\frac{5}{3}
87
7
math
In the polar coordinate system, the curve $\rho=4\sin \left( \theta- \frac{\pi}{3} \right)$ is symmetric about what axis?
\frac{5\pi}{6}
36
9
math
Find the largest positive integer \(n\) for which there exist \(n\) finite sets \(X_{1}, X_{2}, \ldots, X_{n}\) with the property that for every \(1 \leq a<b<c \leq n\), the equation \(\left|X_{a} \cup X_{b} \cup X_{c}\right|=\lceil\sqrt{a b c}\rceil\) holds.
4
94
1
math
Let set $A = \{a, b\}$, and set $B = \{c, d, e\}$. Then, the number of mappings that can be established from $A$ to $B$ is ____, and the number of mappings that can be established from $B$ to $A$ is ____.
9, 8
69
4
math
A truck travels $\frac{b}{4}$ feet every $t$ seconds. There are $2$ feet in a yard. Calculate the number of yards the truck travels in $5$ minutes.
\frac{37.5b}{t}
41
11
math
Consider four functions, each represented by a graph, labelled (2) through (5). The domain of function (3) is now $$\{-6, -5, -4, -3, -2, -1, 0, 1, 2, 3\}.$$ Determine the product of the labels of the functions which are invertible. Assume: - Function (2) is \( y = x^3 - 2x \) on \([-2, 4]\), - Function (3) has discret...
120
245
3
math
(1) Calculate the value of $0.0081^{ \frac {1}{4}}+(4^{- \frac {3}{4}})^2+(\sqrt {8})^{- \frac {4}{3}}-16^{0.75}$; (2) Given $log_{32}9=p$, $log_{27}25=q$, express $lg5$ in terms of $p$ and $q$.
\frac {15pq}{15pq+4}
96
13
math
Let event $A$ be "The line $ax - by = 0$ intersects the circle $(x - 2\sqrt{2})^2 + y^2 = 6$". (1) If $a$ and $b$ are the numbers obtained by rolling a dice twice, find the probability of event $A$. (2) If the real numbers $a$ and $b$ satisfy $(a - \sqrt{3})^2 + (b - 1)^2 \leq 4$, find the probability of event $A$.
\frac{1}{2}
118
7
math
In triangle \(ABC\), angle \(C\) is \(75^\circ\), and angle \(B\) is \(60^\circ\). The vertex \(M\) of the isosceles right triangle \(BCM\) with hypotenuse \(BC\) is located inside triangle \(ABC\). Find angle \(MAC\).
30^\circ
68
4
math
Given that $\alpha$ and $\beta$ are acute angles, $\cos\alpha=\frac{{\sqrt{5}}}{5}$, $\cos({\alpha-\beta})=\frac{3\sqrt{10}}{10}$, find the value of $\cos \beta$.
\frac{\sqrt{2}}{10}
61
11
math
Let event $A$ have a probability of occurring as $\frac{3}{5}$ and event $B$ have a probability of occurring as $\frac{4}{5}$. Determine the smallest interval that necessarily contains the probability $p$ that both event $A$ and event $B$ occur simultaneously. A) $[0, \frac{1}{2}]$ B) $[\frac{1}{4}, \frac{3}{4}]$ C) $[...
[\frac{2}{5}, \frac{3}{5}]
140
14
math
Using the digits 1, 2, 3, 4 only once to form a 4-digit number, how many of them are divisible by 11?
8
35
1
math
Given vectors $\overrightarrow{a}=(2m+1,3,m-1)$ and $\overrightarrow{b}=(2,m,-m)$, and $\overrightarrow{a}\parallel \overrightarrow{b}$, determine the value of the real number $m$.
-2
58
2
math
What is the greatest integer less than 200 for which the greatest common factor of that integer and 72 is 9?
189
28
3
math
If the function $f(x) = x^3 + ax$ has two extreme points on $\mathbb{R}$, then the range of the real number $a$ is ______.
a < 0
39
4
math
Calculate the domain of the function \( f(x) = \log_5(\log_3(\log_2(x^2))) \).
(-\infty, -\sqrt{2}) \cup (\sqrt{2}, \infty)
29
22
math
Among the following propositions, the correct ones are __________. (1) The regression line $\hat{y}=\hat{b}x+\hat{a}$ always passes through the center of the sample points $(\bar{x}, \bar{y})$, and at least through one sample point; (2) After adding the same constant to each data point in a set of data, the variance ...
(2)(6)(7)
292
7
math
If the radius of the top base of a truncated cone is $5$, the radius of the bottom base is $R$, and a section (a plane parallel to the top and bottom bases and equidistant from them) divides the truncated cone into two parts with a ratio of side areas of $1:2$, then $R=\_\_\_\_\_\_.$
25
75
2
math
Let the sum of the first $n$ terms of an arithmetic sequence $\{a_n\}$ be $S_n$. Given that $a_1=2$, and the sequence $\left| \sqrt{S_n} \right|$ is also an arithmetic sequence, find the value of $a_{26}$.
102
66
3
math
Find the degree measure of the smallest positive angle $\theta$ for which \[\sin 10^\circ = \cos 40^\circ - \cos \theta.\]
30^\circ
38
4
math
Given the function $f(x) = \ln x - \frac{1}{2}a(x-1)$ $(a \in \mathbb{R})$. (Ⅰ) If $a=-2$, find the equation of the tangent line to the curve $y=f(x)$ at the point $(1, f(1))$. (Ⅱ) If the inequality $f(x) < 0$ holds for any $x \in (1, +\infty)$, determine the range of the real number $a$.
[2, +\infty)
114
8
math
A book with 53 pages numbered 1 to 53 has its pages renumbered in reverse, from 53 to 1. For how many pages do the new page number and old page number share the same units digit?
11
50
2
math
Form a four-digit number using the digits 1, 2, and 3. Each digit must be used at least once, and the same digit cannot be adjacent to itself. Determine the total number of such four-digit numbers that can be formed.
18
51
2
math
Solve for the ordered pair $(x,y)$ that satisfies the simultaneous equations: \begin{align*} 3x - 4y &= -2, \\ 4x + 5y &= 23. \end{align*}
\left(\frac{82}{31}, \frac{77}{31}\right)
50
22
math
A positive integer \( \overline{ABC} \), where \( A, B, C \) are digits, satisfies \[ \overline{ABC} = B^{C} - A \] Find \( \overline{ABC} \).
127
54
3
math
Two skaters, Allie and Billie, are at points $A$ and $B$, respectively, on a flat, frozen lake. The distance between $A$ and $B$ is $100$ meters. Allie leaves $A$ and skates at a speed of $8$ meters per second on a straight line that makes a $60^\circ$ angle with $AB$. At the same time Allie leaves $A$, Billie leaves $...
160
248
3
math
Find the remainder when \(x^4 + 1\) is divided by \(x^2 - 2x + 4.\)
-8x + 1
28
6
math
Given two circles $O_1: x^2 + y^2 = 5$ and $O_2: (x-m)^2 + y^2 = 5$ ($m \in \mathbb{R}$) intersect at points A and B, and the tangents to the circles at point A are perpendicular to each other, then the length of segment AB is \_\_\_\_\_\_.
\sqrt{10}
86
6
math
Given the sequence: $$( \frac{1}{1}), ( \frac{1}{2}, \frac{2}{1}), ( \frac{1}{3}, \frac{2}{2}, \frac{3}{1}), ( \frac{1}{4}, \frac{2}{3}, \frac{3}{2}, \frac{4}{1}), \ldots, ( \frac{1}{n}, \frac{2}{n-1}, \frac{3}{n-2}, \ldots, \frac{n-1}{2}, \frac{n}{1})$$, denote the elements of the sequence as: $a_1, a_2, a_3, a_4, a_5...
7
178
1
math
Non-zero vectors \(\vec{a}\) and \(\vec{b}\) satisfy \(|\vec{a}| = |\vec{b}| = |\vec{a} - \vec{b}|\). The angle between \(\vec{a}\) and \(\vec{a} + \vec{b}\) is equal to?
30^\circ
73
4
math
Given circle C: x² + y² - 2x = 0, calculate the distance from the center of circle C to the origin O.
1
31
1
math
Given non-zero vectors $\overrightarrow{a}$ and $\overrightarrow{b}$ satisfy $|\overrightarrow{b}|=2|\overrightarrow{a}|=1$, and $\overrightarrow{a}$ is perpendicular to $(\overrightarrow{a}+\overrightarrow{b})$, then the angle between $\overrightarrow{a}$ and $\overrightarrow{b}$ is ______.
\frac{2\pi}{3}
80
9
math
A three-meter gas pipe has rusted in two places. Determine the probability that all three resulting parts can be used as connections to gas stoves, given that according to regulations, a stove should not be located closer than 75 cm to the main gas pipe.
\frac{1}{16}
54
8
math
A rectangular wooden block is 6 inches long, 3 inches wide, and 2 inches high. The block is painted blue on all six sides and then cut into 1 inch cubes. How many of the cubes each have a total number of blue faces that is an even number?
20
58
2
math
If the 200th day of some year is a Sunday and the 100th day of the following year is also a Sunday, what day of the week was the 300th day of the previous year? Provide the answer as the number of the day of the week (if Monday, then 1; if Tuesday, then 2, etc.).
1
78
1
math
If $|a|=6$, $|b|=2$, and $a+b \gt 0$, then the value of $a-b$ is ______.
4 \text{ or } 8
33
8
math
You want to sort the numbers 54321 using block moves. In other words, you can take any set of numbers that appear consecutively and put them back in at any spot as a block. What is the minimum number of block moves necessary to get 12345?
3
62
1
math
For a number $x$, we use $\left(x\right]$ to represent the largest integer less than $x$, for example: $\left(1.6\right]=1$, $\left(-4\right]=-5$. ① Fill in the blanks: $(0 ]=\_\_\_\_\_\_,(-2023 ]=\_\_\_\_\_\_$; ② If $|\left(x\right]-3|=6$, then the range of values for $x$ is ______.
9 < x \leqslant 10 \text{ or } -3 < x \leqslant -2
106
27
math
Given the function $f(x)=\cos 2x+a\sin x+b$ where $a \lt 0$. $(1)$ If the maximum value of $f(x)$ is $\frac{9}{8}$ and the minimum value is $-2$ when $x\in R$, find the values of real numbers $a$ and $b$. $(2)$ If $a=-2$ and $b=1$, and the function $g(x)=m\sin x+2m$ where $x\in[\frac{\pi}{6},\frac{2\pi}{3}]$, and $...
(-\infty, -\frac{2}{3})
151
13
math
A circle of radius 5 is centered at point $B$. An equilateral triangle with a vertex at $B$ has a side length of 10. Find the difference between the area of the region that lies inside the circle but outside the triangle and the area of the region that lies inside the triangle but outside the circle.
25(\pi - \sqrt{3})
67
10
math
If $x > -1$, then when $x=$_______, $f(x)=x+\frac{1}{x+1}$ has its minimum value, which is _______.
1
38
1
math
Write down an integer that is greater than $\sqrt{2}$ and less than $\sqrt{17}$ ____.
3
24
1
math
What is the maximum possible number of rays in a plane emanating from a single point and forming pairwise obtuse angles?
4
24
1
math
Let $n$ be an odd integer with exactly 12 positive divisors. Find the number of positive divisors of $27n^3$.
256
32
3
math
Calculate the result of $\sin 5^{\circ}\cos 55^{\circ}-\cos 175^{\circ}\sin 55^{\circ}$.
\frac{\sqrt{3}}{2}
39
10
math
In a triangle, the larger angle at the base is $45^{\circ}$, and the altitude divides the base into segments of 20 and 21. Find the length of the larger lateral side.
29
45
2
math
Sides $\overline{AJ}$ and $\overline{EF}$ of regular decagon $ABCDEFGHIJ$ are extended to meet at point $Q$. What is the degree measure of angle $Q$?
72^\circ
43
4
math
Consider the simultaneous equations $$ \left\{\begin{array}{l} x y + x z = 255 \\ x z - y z = 224 \end{array}\right. $$ Find the number of ordered triples of positive integers \((x, y, z)\) that satisfy the above system of equations.
2
74
1
math
On the number line, moving point $A$ by $2$ units exactly reaches the point representing $-2$. What number does point $A$ represent?
0 \text{ or } -4
33
8
math
The NIMO problem writers have invented a new chess piece called the *Oriented Knight*. This new chess piece has a limited number of moves: it can either move two squares to the right and one square upward or two squares upward and one square to the right. How many ways can the knight move from the bottom-left square ...
252
100
3
math
Let $x_1 < x_2 < x_3$ be the three real roots of the equation $\sqrt{2020} x^3 - 4041x^2 + 3 = 0$. Find $x_2(x_1+x_3)$.
3
62
1
math
The magnitude of the vector $\overrightarrow{a}+2\overrightarrow{b}$ can be calculated using the given information that the angle between the plane vectors $\overrightarrow{a}$ and $\overrightarrow{b}$ is $60^{\circ}$, $|\overrightarrow{a}|=2$, $|\overrightarrow{b}|=1$.
2\sqrt{3}
75
6
math
Find all pairs of natural numbers \( a \) and \( b \) such that out of the four statements: 5) \( a^2 + 6a + 8 \) is divisible by \( b \); 6) \( a^2 + ab - 6b^2 - 15b - 9 = 0 \); 7) \( a + 2b + 2 \) is divisible by 4; 8) \( a + 6b + 2 \) is a prime number; three are true, and one is false.
(5, 1) \text{ and } (17, 7)
118
18
math
Given that $3\sin a-\cos a=0$ and $7\sin β+\cos β=0$, and also given that $0 < a < \frac{π}{2} < β < π$, determine the value of $2α-β$.
-\frac{3π}{4}
56
8
math
Given two circles are internally tangent at a point, with circles centered at points $A$ and $B$ having radii $7$ and $4$ respectively, find the distance from point $B$ to the point where an internally tangent line intersects ray $AB$ at point $C$.
4
60
1
math
There are \( n \) pieces of paper, each containing 3 different positive integers no greater than \( n \). Any two pieces of paper share exactly one common number. Find the sum of all the numbers written on these pieces of paper.
84
49
2
math
A list of five positive integers has all of the following properties: - The only integer in the list that occurs more than once is $7$, - Its median is $10$, - Its average (mean) is $12$. What is the largest possible integer that could appear in the list?
25
64
2
math
Given the sets $A=\{x| \frac {[x]-1}{x}<0\}$, $B=\{x|x^2-3x-4\leq0\}$, and $C=\{x|\log_{\frac{1}{2}}x>1\}$, and the descriptions from students A, B, and C, determine the value of $[x]$.
1
85
1
math
Five people of heights 65, 66, 67, 68, and 69 inches stand facing forwards in a line. How many orders are there for them to line up, if no person can stand immediately before or after someone who is exactly 1 inch taller or exactly 1 inch shorter than himself?
14
69
2
math
The inclination angle of the line $\sqrt{3}x + y - 1 = 0$ can be calculated using the slope.
120^{\circ}
28
7
math
The set \( A \) consists of integers, with the smallest element being 1 and the largest being 100. Except for 1, every element is equal to the sum of two (not necessarily distinct) elements from the set \( A \). Find the minimum number of elements in set \( A \).
9
65
1
math
How many real solutions are there for \(y\) in the following equation: \[ (2y + 5)^2 - 7 = -|3y + 1| \]
2
40
1
math
Given two vectors $\overrightarrow{a} = \left(\frac{3}{2}, 1+\sin \alpha\right)$ and $\overrightarrow{b} = \left(1-\cos\alpha, \frac{1}{3}\right)$, and $\overrightarrow{a}$ is parallel to $\overrightarrow{b}$, find the acute angle $\alpha$.
45^{\circ}
79
6
math
Selected Exercise $(4-4)$: Coordinate Systems and Parametric Equations Given that in the rectangular coordinate system $xOy$, the equation of the ellipse $(C)$ is $\frac{{y}^{2}}{16}+\frac{{x}^{2}}{4}=1$. Establish a polar coordinate system with $O$ as the pole and the non-negative semiaxis as the polar axis, using th...
9
188
1
math
Find the sum of all divisors \( d \) of \( N = 19^{88} - 1 \) that are of the form \( d = 2^a \cdot 3^b \) where \( a \) and \( b \) are natural numbers.
819
61
3
math
Given that a normal vector of line $l$ is $\overrightarrow{n}=(\sqrt{3}, -1)$, find the size of the slope angle of line $l$.
\frac{\pi}{3}
38
7
math
Given that the centers of two circles are both on the line $x-y+1=0$ and they intersect at two different points. If one of the intersection points is $A(-2, 2)$, then the coordinates of the other intersection point are \_\_\_\_\_\_.
(1, -1)
60
6
math
From the following infinite list of numbers, how many are integers? $$\sqrt{1024},\sqrt[3]{1024},\sqrt[4]{1024},\sqrt[5]{1024},\sqrt[6]{1024},\ldots$$
3
66
1
math
The number of integers whose absolute value is less than 4, their sum, and their product are.
0
21
1
math
Given an arithmetic sequence $\{a\_n\}$ with a common ratio of $q (q > 0)$, let $S_n$ represent the sum of its first $n$ terms. If $S_2 = 3a_2 + 2$ and $S_4 = 3a_4 + 2$, find the value of $q$.
\frac{3}{2}
78
7
math
Jar C initially contains 6 red buttons and 12 green buttons. Michelle removes the same number of red buttons as green buttons from Jar C and places them into an empty Jar D. After the removal, Jar C is left with $\frac{3}{4}$ of its initial button count. If Michelle were to randomly choose a button from Jar C and a but...
\frac{5}{14}
97
8
math
Triangles $PQR$ and $PRS$ are isosceles with $PQ=QR$ and $PR=RS$. Point $R$ is inside $\triangle PQR$, $\angle PQR = 50^\circ$, and $\angle PRS = 130^\circ$. What is the degree measure of $\angle QPR$?
40^\circ
74
4
math
In $\triangle ABC$, the sides opposite to angles $A$, $B$, $C$ are $a$, $b$, $c$ respectively, and $b\cos C=3a\cos B-c\cos B$, $\overrightarrow{BA}\cdot \overrightarrow{BC}=2$, find the area of $\triangle ABC$.
2\sqrt{2}
71
6
math
Given that 10% of the students got 70 points, 25% got 80 points, 20% got 85 points, 15% got 90 points, and the rest got 95 points, calculate the difference between the mean and the median score on this exam.
1
68
1
math
If $|a|=2$, $b^{2}=9$, and $a \lt b$, find the value of $a-b$.
-1 \text{ or } -5
29
9
math
Given a function $f(x)=\ln(\sqrt{1+x^2}-x)+\frac{2}{2^x+1}+1$, if $f(m-1)+f(1-2m) > 4$, then the range of real number $m$ is ______.
(0,+\infty)
63
7
math
An ellipse has foci at $(3, 3)$ and $(3, 7)$, and it passes through the point $(9, -2)$. Write the equation of this ellipse in the standard form \[\frac{(x-h)^2}{a^2} + \frac{(y-k)^2}{b^2} = 1,\] where $a, b, h, k$ are constants, and $a$ and $b$ are positive. Find the ordered quadruple $(a, b, h, k)$.
\left(\frac{\sqrt{61} + \sqrt{117}}{2}, \sqrt{\left(\frac{\sqrt{61} + \sqrt{117}}{2}\right)^2 - 4}, 3, 5\right)
113
59
math
In triangle \( ABC \), given \( a^{2} + b^{2} + c^{2} = 2\sqrt{3} \, ab \, \sin C \), find \( \cos \frac{A}{2} \cos \frac{B}{2} \cos \frac{C}{2} \).
\frac{3\sqrt{3}}{8}
71
12
math
Define a sequence of integers by $T_1 = 2$ and for $n\ge2$ , $T_n = 2^{T_{n-1}}$ . Find the remainder when $T_1 + T_2 + \cdots + T_{256}$ is divided by 255. *Ray Li.*
20
79
2
math
a) In how many different ways can a convex octagon be divided into triangles by diagonals that do not intersect inside the octagon? b) Euler's problem. In how many ways can a convex $n$-gon be divided into triangles by diagonals that do not intersect inside the $n$-gon?
\frac{(2n-4)!}{(n-1)!(n-2)!}
65
20
math
Given the arithmetic sequence $\{a_n\}$, $a_5 > 0$ and $a_4 + a_7 < 0$, find the maximum term in the sum of the first $n$ terms $S_n$ of $\{a_n\}$.
S_5
58
3
math
Given \\(f(x)=x\ln x\\), \\(g(x)=x^{3}+ax^{2}-x+2\\). \\((\\)I\\()\\) If the function \\(g(x)\\) is monotonically decreasing in the interval \\((- \dfrac {1}{3},1)\\), find the expression of function \\(g(x)\\); \\((\\)II\\()\\) Under the condition of \\((\\)I\\()\\), find the equation of the tangent line to the gr...
[-2,+\infty)
185
7
math
The exchange rate of the cryptocurrency Chukhoyn was one dollar on March 1, and then increased by one dollar each day. The exchange rate of the cryptocurrency Antonium was also one dollar on March 1, and then each day thereafter, it was equal to the sum of the previous day's rates of Chukhoyn and Antonium divided by th...
92/91
96
5
math
Assume that $e$, $f$, $g$, and $h$ are positive integers such that $e^5 = f^4$, $g^3 = h^2$, and $g - e = 31$. Determine $h - f$.
971
55
3
math
Elective 4-4: Coordinate System and Parametric Equations In the Cartesian coordinate system $xOy$, the parametric equation of line $l_1$ is $\begin{cases}x=2+t \\ y=kt\end{cases}$ (where $t$ is the parameter), and the parametric equation of line $l_2$ is $\begin{cases}x=-2+m \\ y= \frac{m}{k}\end{cases}$ (where $m$ is...
\sqrt{5}
241
5
math
There is a tetrahedron with vertices $P$, $Q$, $R$, and $S$. The length of the shortest trip from $P$ to $R$ along the edges is the length of 4 edges. How many different 4-edge trips are there from $P$ to $R$?
4
65
1
math
Given the sequence $\{a\_n\}$ that satisfies $a_{n+1} - a_{n} = 2$, where $n \in \mathbb{N}^*$, and $a_{3} = 3$, find $a_{1} =$\_\_\_\_\_\_ and its first $n$ terms sum $S_{n} =$\_\_\_\_\_\_.
S_{n} = n^2 - 2n
87
12
math
Use the Euclidean algorithm to find the greatest common divisor of 5280 and 12155.
55
25
2
math
For arithmetic sequences $\{a_n\}$ and $\{b_n\}$, the sums of the first $n$ terms of $\{b_n\}$ are denoted as $S_n$ and $T_n$, respectively. For all natural numbers $n$, it holds that $$\frac {S_{n}}{T_{n}} = \frac {n}{n+1}$$. Evaluate $\frac {a_{5}}{b_{5}}$.
\frac{9}{10}
96
8
math
Given that $P$ is a moving point on the line $3x+4y+8=0$, $PA$ and $PB$ are two tangents of the circle $x^{2}+y^{2}-2x-2y+1=0$, $A$ and $B$ are the points of tangency, and $C$ is the center of the circle. Find the minimum value of the area of quadrilateral $PACB$.
2\sqrt{2}
97
6
math
Convex quadrilateral $ABCD$ has $AB = 9$ and $CD = 12$. Diagonals $AC$ and $BD$ intersect at $E$, $AC = 14$, and $\triangle AED$ and $\triangle BEC$ have equal areas. What is $AE$?
6
67
1
math
Anna flips an unfair coin 10 times. The coin has a $\frac{1}{3}$ probability of coming up heads and a $\frac{2}{3}$ probability of coming up tails. What is the probability that she flips exactly 7 tails?
\frac{5120}{19683}
53
14
math
Given the right triangles ABC and ABD, what is the length of segment BC, in units? [asy] size(150); pair A, B, C, D, X; A=(0,0); B=(0,15); C=(-20,0); D=(-45,0); draw(A--B--D--A); draw(B--C); draw((0,2)--(-2,2)--(-2,0)); label("$50$", (B+D)/2, NW); label("$25$", (C+D)/2, S); label("$20$", (A+C)/2, S); label("A", A, SE);...
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